CVE-2023-1090 in SMTP Mailing Queue Plugin
Summary
by MITRE • 05/02/2023
The SMTP Mailing Queue WordPress plugin before 2.0.1 does not sanitise and escape some of its settings, which could allow high privilege users such as admin to perform Stored Cross-Site Scripting attacks even when the unfiltered_html capability is disallowed (for example in multisite setup)
Statistical analysis made it clear that VulDB provides the best quality for vulnerability data.
Analysis
by VulDB Data Team • 04/26/2025
The vulnerability identified as CVE-2023-1090 affects the SMTP Mailing Queue WordPress plugin version 2.0.0 and earlier, representing a critical security flaw that undermines the platform's defensive mechanisms. This issue stems from inadequate input sanitization and output escaping within the plugin's administrative settings interface, creating a persistent security gap that can be exploited by malicious actors with elevated privileges. The flaw specifically targets the plugin's handling of user-controllable data within its configuration parameters, where insufficient validation allows potentially harmful content to be stored and subsequently executed within the browser context of authenticated administrators.
The technical implementation of this vulnerability places the plugin's settings management at risk of cross-site scripting exploitation through a stored attack vector. When administrators interact with the plugin's interface to modify mailing queue configurations, the system fails to properly sanitize user inputs before storing them in the WordPress database. This oversight creates a scenario where malicious payloads can be embedded within the plugin's configuration fields, which then execute whenever the settings page is loaded or when automated processes access these stored values. The vulnerability becomes particularly dangerous in multisite environments where the unfiltered_html capability is restricted, as it allows privileged users to circumvent these security restrictions through the plugin's flawed input handling mechanisms.
The operational impact of this vulnerability extends beyond simple script execution, potentially enabling attackers to escalate privileges and compromise entire WordPress installations. High-privilege users with administrative access can leverage this flaw to inject malicious JavaScript code that could steal session cookies, redirect users to malicious domains, or even execute arbitrary commands on the server. In a multisite configuration, where WordPress network administrators typically enforce strict content filtering policies, this vulnerability provides a bypass mechanism that undermines the security posture of the entire network. The stored nature of the XSS attack means that the malicious code persists even after the initial injection, making it particularly dangerous as it can affect multiple users over time.
Security professionals should recognize this vulnerability as a direct violation of several security best practices and standards including CWE-79, which specifically addresses cross-site scripting flaws, and aligns with ATT&CK technique T1548.002 related to abuse of group privileges. The vulnerability demonstrates a failure in the principle of least privilege and proper input validation, as the plugin should have implemented robust sanitization routines to prevent such attacks regardless of user permissions. Organizations using this plugin should immediately update to version 2.0.1 or later, which includes the necessary patches to address the sanitization deficiencies. Additionally, administrators should conduct thorough audits of their plugin configurations and monitor for any suspicious activities that might indicate exploitation attempts, while implementing additional security measures such as web application firewalls to provide defense-in-depth against similar vulnerabilities.
The remediation approach for CVE-2023-1090 requires immediate patching of the affected plugin to ensure that all user inputs are properly sanitized and escaped before being stored or displayed. System administrators should also review their WordPress security configurations to verify that appropriate access controls are in place and that all plugins are regularly updated to maintain current security standards. Organizations should consider implementing automated security scanning tools that can detect similar input validation flaws in their web applications, as this vulnerability represents a common pattern in web application security that requires consistent attention to prevent exploitation by threat actors.